Adding a Display Link
Display links are a kind of timer that synchronizes drawing to a display’s refresh rate. You can adjust this frame refresh time by changing the display link’s frameInterval property. It defaults to 1. A higher number slows down the refresh rate. Setting it to 2 halves your frame rate. Create the display link when a screen connects to your device. The UIScreen class implements a method that returns a display link object for its screen. You specify the target for the display link and a selector to call.
The display link fires on a regular basis, letting you know when to update the Video Out screen. You can adjust the interval up for less of a CPU load, but you get a lower frame rate in return. This is an important trade-off, ...
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